Differential output structure with reduced skew for a single input

Abstract

The invention provides an improved differential output structure with minimal skew and introduces less process variations. According to one embodiment of the invention, a differential output structure is provided and comprises an input line, an output driver and a sync circuit. The input line includes first and second paths. The first path has an input end for receiving input signals. The first path also has an output end and includes at least one driving element. The second path has an input end operably coupled to the input end of the first path for receiving the input signals. The second path also has an output end. The output driver is operably coupled to the output ends of the first and second paths and is configured to provide differential outputs. The sync circuit is operably coupled between the first and second paths and is configured to synchronize the speed of signals traveling on the two paths.

What is claimed is:  
     
       1. A differential output structure, comprising: 
       an input line including:  
       a first path having an input end for receiving an input signal, the first path also having an output end and including at least one driving element, and  
       a second path having an input end and operably coupled to the input end of the first path for receiving the input signal, the second path also having an output end;  
       an output driver, operably coupled to the output ends of the first and second paths, that is configured to provide differential outputs; and  
       a bi-directional sync circuit, operably coupled between the first and second paths, which is configured to synchronize the speed of signals traveling on the two paths to arrive at the output driver by dynamically synchronizing the two paths bi-directionally through the sync circuit; the bi-directional sync circuit having a single connection to the first path and a single connection to the second path and being sized in accordance with relative connection positions in the first and second paths.  
     
     
       2. The structure of  claim 1 , 
       wherein the first path further includes a plurality of driving elements connected in series to one another, the first path providing an inverted output of the input signal and  
       wherein the second path includes a plurality of driving elements connected in series to one another, the second path providing a non-inverted output of the input signal.  
     
     
       3. The structure of  claim 2 , wherein the driving elements of the first and second paths have a predetermined constant taper ratio. 
     
     
       4. The structure of  claim 2 , wherein each sync circuit is coupled between an output of a driving element on the first path having a first current driving capability and an output of a driving element on the second path having a second current driving capability, and—wherein the first current driving capability is greater than the second current driving capability. 
     
     
       5. The structure of  claim 1 , further includes at least another sync circuit, operably coupled between the first and second paths, that is configured to synchronize the speed of signals traveling on the two paths. 
     
     
       6. The structure of  claim 5 , wherein each of the sync circuits includes a capacitances. 
     
     
       7. The structure of  claim 1 , wherein the sync circuit includes a capacitance. 
     
     
       8. The structure of  claim 1 , wherein the sync circuit is coupled between the output ends of the first and second paths. 
     
     
       9. The structure of  claim 1 , wherein the sync circuit dynamically synchronizes the two paths by slowing down a faster of the two paths such that the signals of the two paths arrive at the output driver at substantially a same time. 
     
     
       10. A differential output structure, comprising: 
       an input line including:  
       a first path having an input end for receiving an input signal, the first path also having an output end and including at least one driving element, and  
       a second path having an input end and operably coupled to the input end of the first path for receiving the input signal, the second path also having an output end and including at least one driving element;  
       an output driver, operably coupled to the output ends of the first and second paths, that is configured to provide differential outputs; and  
       a plurality of bi-directional sync circuits, operably coupled between the first and second paths, which are configured to synchronize the speed of signals traveling on the two paths to arrive at the output driver by bidirectionally synchronizing the two paths through the sync circuits;  
       the bi-directional sync circuits each having a single connection to the first path and a single connection to the second path, the sync circuits being sized relative to their position along each of the first and second paths and the connections being disposed between respective driving elements.  
     
     
       11. The structure of  claim 10 , 
       wherein the first path further includes a plurality of driving elements connected in series to one another, the first path providing an inverted output of the input signal and  
       wherein the second path includes a plurality of driving elements connected in series to one another, the second path providing a non-inverted output of the input signal.  
     
     
       12. The structure of  claim 11 , wherein the driving elements of the first and second paths have a predetermined constant taper ratio. 
     
     
       13. The structure of  claim 11 , wherein each sync circuit is coupled between an output of a driving element on the first path having a first current driving capability and an output of a driving element on the second path having a second current driving capability, and wherein the first current driving capability is greater than the second current driving capability. 
     
     
       14. The structure of  claim 10 , further includes at least another sync circuit, operably coupled between the first and second paths, that is configured to synchronize the speed of signals traveling on the two paths. 
     
     
       15. The structure of  claim 14 , wherein each of the sync circuits includes a capacitance. 
     
     
       16. The structure of  claim 10 , wherein the sync circuit includes a capacitance. 
     
     
       17. The structure of  claim 10 , wherein the sync circuit is coupled between the output ends of the first and second paths. 
     
     
       18. The structure of  claim 10 , wherein the sync circuit bidirectionally synchronizes the two paths by slowing down a faster of the two paths such that the signals of the two paths arrive at the output driver at substantially a same time. 
     
     
       19. A differential output structure, comprising: 
       an input line including:  
       a first path having an input and including at least one driving element, and  
       a second path operably coupled to the first path at the input end for receiving an input signal;  
       an output driver, operably coupled to output ends of the first and second paths; and  
       a bi-directional sync circuit, operably coupled between the first and second paths, which is configured to synchronize the speed of signals traveling on the two paths to arrive at the output driver by bidirectionally synchronizing the two paths through the synch circuit to slow a faster of the two paths, the bi-directional sync circuit having a single connection to the first path and a single connection to the second path and being sized in accordance with relative connection positions in the first and second paths.  
     
     
       20. The structure of  claim 19 , wherein the faster the two paths is slowed such that the signals of the two paths arrive at the output driver at substantially a same time.